Why does my standard viewer just display a red x on the page?
Why does my browser keep telling me to install Flash even though I already have it installed?
Check to see if you have update KB4577586 in add/remove programs. If you do, this is why it stopped working. If you need Flash enabled again, then please follow directions in the "summary" section of the help link below:
Microsoft released update KB4577586 at the end of October that removes/disables Flash. Per the details from Microsoft, update 4577586 cannot be uninstalled.
For more information see: https://support.microsoft.com/en-us/help/4577586/update-for-removal-of-adobe-flash-player